Pump apparatus

ABSTRACT

Vessels ( 10, 11, 12  and  13 ) are associated with an inlet manifold ( 14 ) passing to inlets ( 16 ), each controlled by a knifegate valve ( 17 ). The lower ends of the pots ( 10 ) and ( 12 ), and pots ( 11 ) and ( 13 ), pass material through respective outlet knifegate valves ( 22 ) to respective first ( 23 ) and second ( 24 ) delivery lines. The respective knifegate valves ( 17 ) and outlet knifegate valves ( 22 ) of pots ( 10 ) and ( 11 ) on the one hand and pots ( 12 ) and ( 13 ) on the other, are operable by respective common pneumatic actuators ( 25 ). Each pot has an ejector assembly ( 26 ) having an upper chamber ( 28 ), an air injector nozzle ( 30 ), and an accelerator tube ( 31 ) to create the venturi function. An air cycling valve ( 32 ) transitions the upper chamber ( 28 ) between a depressurized space and a pressurized space. The accelerator tube ( 31 ) exhausts to a delivery line ( 23  or  24 ). Ejector assembly ( 26 ) air is supplied via air control valve ( 35 ). The respective delivery lines ( 23 ) and ( 24 ) each have an eductor port ( 37 ) which allow for air to be ported into the line. The completed load and discharge cycle is governed by a pneumatic PLC and pneumatic timers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a filing under 35 U.S.C. 371 of InternationalApplication No. PCT/AU2007/001107, filed Aug. 8, 2007 and entitled “PumpApparatus,” which application is incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

This invention relates to pump apparatus.

This invention has particular but not exclusive application to pumpapparatus for pumping wet slurries of particulates, and for illustrativepurposes reference will be made to such application. However, it is tobe understood that this invention could be used in other applications,such as the pumping of liquids and wet or dry entrainable particulatesgenerally, such as transporting wet, damp or dry solids, muddy products,slurries and liquids and grains.

BACKGROUND OF THE INVENTION

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgement or any form of suggestion that thereferenced prior art forms part of the common general knowledge inAustralia.

PRIOR ART

Drilling for exploration and recovery is often done using drillingfluids to entrain the drill chips. Drill chippings may be screened outof the fluids either to recover the fluids for recycling for their ownvalue or to simply maintain water balance. In either case there remainthe drill chippings that form a slurry or wet gravel of chippings ofvarying fluidity. These chippings need to be moved about. The chippingsform a mass that is invariably highly abrasive, and often either or bothhot and chemically reactive.

Belt and auger conveyors are not constraining of the material and/orhave a high maintenance requirement. Impeller pumps of are less thansuitable due to the impeller coming into contact with the abrasivemixtures.

WO/2006/037186 describes pump apparatus including a housing having amaterial inlet for a material to be pumped and a delivery outlet, avalve on each of the inlet and outlet, and control means for selectivelyopening and closing the respective valves and cycle the pressure in thehousing. When the pressure is low in the housing while the inlet valveis open, material is admitted to housing. When the control means effectsclosure of the inlet valve, the housing is pressurized and the outletvalve is open to discharge said material from said housing. The pressurecycling is achieved with compressed air and a venturi. This apparatuscan be entirely pneumatic in operation, avoiding reliance on electronicsfor its fundamental operation.

The control means is all pneumatic and operates an ejector assemblywhich comprises the venturi adapted to cyclically reduce the housingpressure. The venturi waste air vents into the delivery line downstreamof the outlet valve to provide additional delivery impetus. Thecompressed air supply to the ejector body is valved under control toswitch from applying vacuum to the housing for the inlet phase of thecycle to supplying pressure to housing for the discharge phase.

It is a feature of drilling operations, and particularly of offshoredrilling operations, is that there is effectively no process storagecapacity. The volumes shifted are relatively large and variable. Whilethe above apparatus is controllable over a narrow range of throughputsby control of cycle times and source air pressure, a single apparatuscannot be expected to deal with a wide range of throughputs. Thetechnical solution applied is to mount as many apparatus of “pots” asthe maximum expected throughput demands. In order to eliminate expertmanagement of throughput, the pots are generally set to operate atoptimum, irrespective of actual demand.

This approach has several disadvantages. The size of air plant requiredto run the multiple pots all of the time increases the footprint andespecially the energy requirement. The lack of true integration does notallow an operator flexible control over both the throughput and theenergy expended to transfer drill cuttings within a containment systemas a variable drill program requires. The dynamics of simple of pairingof pots results in one system inevitably slaving to the other, reducingline velocities.

Accordingly, there is a need for a pumping arrangement that can copewith a variation of demand while maintaining reasonable energyconsumption.

SUMMARY OF THE INVENTION

In one aspect the present invention resides broadly in pump apparatusincluding at least one group of pumping elements, each pumping elementcomprising a housing having a material inlet, a discharge outlet to arespective delivery line, and control means controlling actuatorsoperating a valve on each of the material inlet and discharge outlet, acompressed air supply delivering cyclically to a venturi to reduce thehousing pressure for charging and to the housing for pressure discharge,the venturi working air venting into the delivery line downstream of itsclosed outlet valve, the control means being operable to select whichpumping elements are in use and the relative cycle phase of each pumpingelement in use.

Having the venturi working air discharge into the delivery line duringthe vacuum drawdown of the housing has several advantages. The venturiis effectively muffled, reducing the operating noise significantly. Asthe mass transfer effect of the pressure discharge causes a largereduction in pressure in the delivery line after outlet valve closure,there is little or no stalling of the venturi by back pressure. In themultiple-element apparatus of the present invention, the ability toexhaust the venturi to the discharge line is preserved by usingdifferent discharge lines for each member of the group, enabling themembers of the group to be operated out of phase.

The group of pumping elements may include one pot per delivery line ormay include multiple pots per delivery line. There may be providedmultiple pumping elements which selectively deliver in phase to adelivery line so as to provide scalability of throughput on thatparticular delivery line. The delivery line may be provided with airinjection means to supplement the pressure discharge. For example, afterpressure discharge and closing of the outlet valve, high pressure airmay be directed into the delivery line to add impetus to the material inthe line. Thereafter, the additional air is shut off and the linepressure allowed to drop before the venturi is valved on and exhaustedto the delivery line.

The inlets of the pumping elements may be manifolded together to drawfrom a common hopper or other material supply. The manifold may be inthe form of a chamber that will be in a substantially constant state ofreduced pressure by virtue of the out-of-phase operation of the group.The manifold may be associated with a storage means for accumulatingproduct prior to pumping. The system is capable of drawing a head ofproduct. However it is preferred that the material be delivered from ahopper in order to provide some gravity-assist and to minimize the meanfree path for air through the product, thus maximizing the vacuumefficiency.

The housing or pot may be any suitable pressure vessel. The housings arepreferably oriented with the inlets in the top and the delivery outletat the bottom to provide gravity assistance to charge and discharge.This vertical orientation, coupled with a choice of shape anddimensions, may assist in optimizing throughput for a given footprint.The pressure vessel comprising the housing may be optimized for pressurekeeping for a given wall thickness. For example the housing may becylindrical with part-spherical or other rounded ends to resist pressuredeformation. The lower end of the housing may include an inverted conewith the outlet at the apex to optimize gravity assistance in dischargethrough the outlet. The pressure vessel may be optimized for pressurekeeping and have an internal cone fitted for optimizing flow.

The vessel orientation being vertical also allows for a much wider rangein the moisture content of any material being recovered and transferred.

The inlet and outlet valves may each comprise a knifegate-type valve.The actuators for the valves are preferably pneumatic in operation. Theinlet and outlet valves of a particular pumping element may beoperationally interconnected to effect the cyclic operation of therespective valves for the charge and discharge of the pot. Theoperational interconnection may be mechanical, such as by means of acommon double-action actuator.

Alternatively, the respective pairs of material inlet and dischargevalves of adjacent pumping elements may be operationally interconnectedfor alternate operation to effect a lock-stepping of out-of-phaseoperation of the respective pots. The operational interconnection may bemechanical, such as by means of respective common double-actionactuators.

The compressed air driven venturi may form part of an ejector assembly.The ejector assembly may include an elongate body including alow-restriction upper chamber narrowing to an accelerator tube. Theventuri effect may be provided by an injector nozzle directing highpressure air from the air supply across the upper chamber into theaccelerator tube, lowering the pressure in the upper chamber. The upperchamber may be in fluid communication with the top portion of thehousing to effect a reduction in pressure in the housing. The air supplyto the injector nozzle may be switched by an air control valve. The aircontrol valve may be open through both the charge and discharge parts ofthe cycle, and may be closed to disable the pumping element when it isnot required.

The injector nozzles and accelerator tubes (or diffusers) may be one ormore of variable and interchangeable. By this means the configurationmay be matched to the available air, so the unit can be arranged tomaintain the same level of vacuum with more or less air. The volume of“entrapped air” may also be varied. A larger nozzle and itscorresponding accelerator tube may create higher in-line velocities.Alternatively, a selected vacuum may be matched to a particularapplication, such as maintaining 25″Hg vacuum throughout a range ofoperation.

The change over from the air supply generating vacuum to the air supplypressurizing the housing may be by any suitable switching means. Forexample, there my be provided a selectable diverter upstream of theventuri and adapted to alternately switch the air supply between theventuri and a pressurizing inlet to the housing. Alternatively, thepreferred ejector assembly may include a cycling valve across theaccelerator tube or venturi exhaust and operable to alternately open andocclude the venturi exhaust path. An open cycling valve closure allowsthe venturi to operate and reduce pressure in the housing. A closedcycling valve stalls the venturi, closes off the venturi exhaust path tothe delivery line, and pressurizes the upper chamber and housing.

The effect is that while the air control valve is open, and both theinlet and cycling valve are open and the outlet valve closed, materialis charged into the housing under vacuum. By the simple expedient ofclosing the inlet valve, opening the outlet valve and switching thecycling valve to closed, the venturi is stalled and the housingpressurized to expel the housing contents at velocity into the deliveryline.

While the outlet valve is closed for developing the charge vacuum, theventuri working air exhausts into the delivery line downstream of theclosed outlet valve. It is highly desirable that the pots operating on agiven delivery line are substantially synchronous. In order to obtainconstant draw and enable operation at average air consumption instead ofa peak, it is preferred that pots on separate delivery lines areoperated evenly out of phase. In the case of systems having two deliverylines, pneumatic, hydraulic or mechanical linking of the inlet valves ofpots on alternate delivery lines may ensure that when one is open theother is closed, and likewise for the outlet valves. Limit switchesassociated with the inlet and/or outlet valves may be used to ensurethat the valves are appropriately set before the control means operatesthe cycling valve.

The control means may comprise one or more integrated or independentcontrollers controlling a hierarchy of functions. The control means mayinclude one or more of electronic and pneumatic controllers. Thecontroller may comprise a programmable logic controller (PLC). The PLCmay be a 100% pneumatic PLC to avoid electronics. The control means maycontrol directly or indirectly any one or more of the functions ofcharge volume control, discharge volume control, pot on/off control, airpressure regulation, inlet and outlet valve timing, venturi operationand housing pressurization control.

The controller may control the respective element operating phase by anysuitable means. While out of phase locking by interconnection of inletvalves and interconnection of outlet valves is described above, itfollows that phase control will require a different approach where therespective valves are not so linked. For example, the inlet and outletvalves of each pot may be interconnected for operation by a doubleacting pneumatic actuator and each actuator may be under the operationalcontrol of an air distributor function of the control means whichensures that the phase is controlled.

The controller may tap air from the air supply to power pneumatic timersfor process timing control. For example a pneumatic timer may control anactuator or air solenoid to direct air to the preferred knifegate valveactuator and an actuator for the preferred valve changing the venturifrom its vessel evacuating mode to its vessel-pressurizing mode. Thepreferred pneumatic PLC may include integrated timer functions, or maycontrol external timers. The air control valve controlling the supply ofair to the apparatus may be subject to switch means associated with theknifegate valve so the knifegate valves must be full open or closedbefore the air does its work either drawing vacuum or pressurizing thehousing. While the timers control the timing, the switch means ensurethat a respective knifegate is fully made one way or the other prior toallowing air through the system.

The control means may control the amount of material admitted to thehousing for each cycle by any suitable means. For example the controllermay include a timer function and the charge may be determined on anempirically determined time basis having regard to the nature of thematerial. Alternatively, the charge may be metered by weight, where atransducer or the like cooperates with the control means, or by volume,such as by a paddlewheel in the inlet supply.

In a further aspect the invention resides broadly in a scalable-outputpump pack including an inlet manifold accepting material at a variablerate, at least one group of pumping elements each comprising a housinghaving a material inlet drawing from said manifold, a discharge outletto a respective delivery line, and pneumatic control means controllingactuators operating a valve on each of the material inlet and dischargeoutlet, a compressed air supply delivering cyclically to a venturi toreduce the housing pressure for charging and to the housing for pressuredischarge, the venturi working air venting into the delivery linedownstream of its closed outlet valve, the control means being operableon the air supply to select which pumping elements are in use, and beingoperable to control said cyclic delivery and actuators to operatepumping elements discharging to a delivery line in phase, and to operatepumping elements discharging to different delivery lines out of phase.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the followingnon-limiting embodiment of the invention as illustrated in the drawingsand wherein:

FIG. 1 is plan view of apparatus in accordance with the presentinvention; and

FIG. 2 is an elevation of the apparatus of FIG. 1.

In the figures there is provided a pump apparatus adapted to bepallet-mounted and comprising four pressure vessels (10, 11, 12 and 13)or pots, arranged on a square footprint. An inlet manifold (14) issupported above the pots and passes material from a central 200 mm topflanged access port (15) to respective 80 mm pot inlets (16), eachcontrolled by an inlet knifegate valve (17). The lower end of thepressure vessels (10, 11, 12 and 13) are each provided with an invertedconical-wall collector (20) passing material into an outlet (21)controlled by an outlet knifegate valve (22). The outlets (21) of pots(10) and (12) pass into a first delivery line (23). The outlets (21) ofpots (11) and (13) pass into a second delivery line (24).

The inlet knifegate valves (17) of pots (10) and (11) are interconnectedand operable by a common, double acting pneumatic actuator (25). Theoutlet knifegate valves (22) of pots (10) and (11) are alsointerconnected and operable by a common, double acting pneumaticactuator (25). Similarly the inlet knifegate valves (17) of pots (12)and (13) are interconnected and operable by a common, double actingpneumatic actuator (25). The outlet knifegate valves (22) of pots (12)and (13) are also interconnected and operable by a common, double actingpneumatic actuator (25).

Each pot (10, 11, 12 and 13) has an ejector assembly (26) bolted up to aflanged opening (27) in the top of the pot. The ejector assembly (26)has an upper chamber (28) forming a downward-turn conduit from theflanged opening (27). An air injector nozzle (30) is directed downwardthrough the sidewall of the upper chamber (28). The lower end of theupper chamber (28) transitions to a relatively narrow accelerator tube(31) aligned with the air injector nozzle (30) to create the venturifunction. An air cycling valve (32) is interposed in the acceleratortube (31) to transition the upper chamber (28) between a depressurizedspace and a pressurized space. The accelerator tube (31) exhausts to anexpansion conduit (33) which in turn dumps to its respective deliveryline (23 or 24).

The air injector nozzle (30) of each ejector assembly (26) is suppliedby air from a compressed air supply line (34) via a respective aircontrol valve (35). The air control valve (35) comprises the on-offswitch for taking its respective pot off-line. The compressed air supplyline (34) includes a manual shut off ball valve (36) enabling the wholeapparatus to be shut down at a single point.

Compressed air is supplied to the compressed air supply line (34) whichinturn supplies air to the air control valves (35) and pneumatic controland circuitry located within an enclosure. If pressure vessels (10) and(12) are assumed to be in the vacuum part of the operating phase, theinlet knifegate valves (17) are ported open to the inlet manifold (14)whilst pressure vessels (11) and (13) and remain isolated from the inletmanifold (14) via their corresponding inlet knifegate valves (17). Withall four air control valves (35) selected ON, air is ported via flexiblemanifold lines to each air injector nozzle (30). As pressure vessels(10) and (12) are in vacuum mode, their respective air cycling valves(32) are open allowing air to pass through the air injector nozzle (30)down the accelerator tube (31) thus generating and drawing a vacuum onpressure vessels (10) and (12), equalized at the inlet manifold (14).Exhaust air from the accelerator tube (31) is allowed to expand into theexpansion conduit (33) and then directed into the first delivery line(23).

Correspondingly air directed to pressure vessels (11) and (13) viacompressed air supply line (34) and air control valves (35) travelsthrough the upper chamber (28) from the air injector nozzle (30) in eachcase, but is halted at air cycling valves (32) and thus redirected backinto the pressure vessels (11) and (13), exerting pressure on, andexpelling the contents. The contents are discharged through the seconddelivery line (24).

The respective delivery lines (23) and (24) each have a small solenoidcontrolled eductor port (37) which allow for air to be ported into theline to aerate the product and boost the in-line conveyor speed ifrequired. The eductor ports (37) are controlled via separate switcheswithin the control enclosure. The completed load and discharge cycle isgoverned by pneumatic timers which allow for variable cycle lengthsdepending on the materials viscosity.

It is to be understood that pots (10) and (11) on the one hand and pots(12) and (13) on the other hand, work in tandem. That is, with pot (10)and pot (12) having their knifegate valves (17, 22) in the dischargepart of the cycle, pots (11) and (13) are in the load part of the cycle.

When compressed air is supplied to the compressed air supply line (34),any individual air control valve (35) can be enabled. Air is also portedto energise the control system including control solenoids. In normaloperation with air control valve (35) to pot (10) selected to the openposition, the air travelling through the upper chamber (28) topressurize the pot (10) also passes through a discharge timer,activating it in the process. The air then actuates a control solenoidwhich ports air to the closed side of the inlet knifegate valve (17)relative to pot (10) and the open side of the outlet knifegate valve(22) along with actuating air cycling valve (32) closed. Air is tappedoff the main manifold to supply pneumatic timers which control the mainsolenoid which in turn directs air to both the knifegate (17) and aircycling (32) valve actuators.

The air control valve (35) that controls the supply to the air injectornozzle (30) gets its actuation signal from a microswitch associated witheach knifegate valve. When the switch contact is made via a striker pin,a spring closes the air control valve (35) between each cycle (load anddischarge). This way the knifegate valves must be full open or closedbefore the air does its work either drawing vacuum or pressurizing thehousing. When the compressed air is halted at the air cycling valve (32)and redirected via the upper chamber (28) back into pot (10) where thecontents are expelled under pressure.

When the discharge timer attached to the inlet knifegate valve (17)times out, the signal to the control solenoid is halted and it returnsto its default position. This in turn ports air to the open side of theinlet knifegate valve (17) and closed side of the outlet knifegate valve(22) relative to the pot (10). Air then passes through a load timerwhich actuates a timer solenoid and ports air to the air control valve(35). This allows flow through the air cycling valve (32) allowing theventuri effect to draw a vacuum on pot (10). Pot (11) is now in thedischarge cycle. When the load timer times out the cycle is repeateduntil the air supply is terminated.

Apparatus in accordance with the foregoing embodiment allow an operatorflexible control over both the throughput and the energy expended totransfer drill cuttings within a containment system as a variable drillprogram requires. This is accomplished by offering the operatorindividual pot control, with each pot capable of delivering up to10,000+ litres per hour either wet or dry cuttings and requiring only150 CFM of air, delivering a more manageable and energy efficientsystem. A performance benefit of this system is the increased in-lineair flow generated by the twin pot function. In a normal dual venturiprocess, one system would inevitably slave to the other, the aboveembodiment's configuration avoids this and delivers greater in-lineconvey velocities.

It will of course be realised that while the above has been given by wayof illustrative example of this invention, all such and othermodifications and variations thereto as would be apparent to personsskilled in the art are deemed to fall within the broad scope and ambitof this invention as is set forth in the claims appended hereto.

1. A pump apparatus including: a first pumping element, the firstpumping element comprising: a first housing having a first materialinlet, and a first discharge outlet to a first delivery line, a secondpumping element, the second pumping element comprising: a second housinghaving a second material inlet, a second discharge outlet to a seconddelivery line, a first venturi associated with the first housing; asecond venturi associated with the second housing: a controller, thecontroller controlling actuators operating a first inlet valve on thefirst material inlet, a second inlet valve on the second material inlet,a first discharge valve on the first discharge outlet, a seconddischarge valve on the second discharge outlet, wherein the controlleris configured to control the first inlet valve, the second inlet valve,the first discharge valve, and the second discharge valve such that:when the first pumping element and the second pumping element are bothin operation, the first pumping element and the second pumping elementeach alternate between a load phase and a discharge phase whereinalternation between the load phase and the discharge phase by the firstpumping element and the second pumping element is out of phase, and whenonly one of the first pumping element or the second pumping element isin operation, only one of the first pumping element and the secondpumping element will alternate between the load phase and the dischargephase; and a compressed air supply delivering cyclically to: the firstventuri to reduce the first housing pressure for charging and to thefirst housing for pressure discharge, the second venturi to reduce thesecond housing pressure for charging and to the second housing forpressure discharge.
 2. A pump apparatus according to claim 1, furthercomprising: a third pumping element, the third pumping elementcomprising: a third housing having a third material inlet, and a thirddischarge outlet to the first delivery line, a fourth pumping element,the fourth pumping element comprising: a fourth housing having amaterial inlet, a fourth discharge outlet to the second delivery line,wherein the third pumping element is configured to selectively deliverin phase with the first pumping element to the first delivery line andthe fourth pumping element is configured to selectively deliver in phasewith the second pumping element to the second delivery line.
 3. A pumpapparatus according to claim 1, wherein the first delivery line, thesecond delivery line, or both includes air injection means directinghigh pressure air into the delivery line to add impetus to the materialin the line.
 4. A pump apparatus according to claim 1, wherein the firstmaterial inlet and the second material inlet are manifolded together todraw from a common material supply.
 5. A pump apparatus according toclaim 4, wherein the manifold is in the form of a chamber that is in asubstantially constant state of reduced pressure by virtue ofout-of-phase operation of the first pumping element and the secondpumping element.
 6. A pump apparatus according to claim 4, wherein themanifold is associated with a storage means for accumulating productprior to pumping.
 7. A pump apparatus according to claim 6, wherein thestorage means is a hopper configured to provide some gravity-assist andto minimize the mean free path for air through the product.
 8. A pumpapparatus according to claim 1, wherein the first housing, the secondhousing, or both are configured such that the first material inletand/or the second material inlet is in the top and the first dischargeoutlet, the second discharge outlet, or both are configured at thebottom to provide gravity assistance to charge and discharge.
 9. A pumpapparatus according to claim 8, wherein the lower end of the firsthousing, the second housing, or both includes an inverted cone with thefirst discharge outlet and/or the second discharge outlet at the apex tooptimize gravity assistance in discharge through the outlet.
 10. A pumpapparatus according to claim 9, wherein the first housing, secondhousing, or both is a pressure vessel optimized for pressure keeping andhas a portion internal to said inverted cone fitted for optimizing flow.11. A pump apparatus according to claim 1, wherein the first and secondmaterial inlets and the first and second discharge outlets each comprisea knifegate-type valve.
 12. A pump apparatus according to claim 1,wherein the first and second material inlets and the first and seconddischarge outlets each comprise pneumatic actuators.
 13. A pumpapparatus according to claim 1, wherein the first material inlet and thefirst discharge outlet, the second material inlet and the seconddischarge outlet, or both are operationally interconnected to effect thecyclic operation of the first pumping element, the second pumpingelement, or both.
 14. A pump apparatus according to claim 13, whereinthe operational interconnection is mechanically by means of a commondouble-action actuator.
 15. A pump apparatus according to claim 1,wherein the first material inlet and the second material inlet, thefirst discharge outlet and the second discharge outlet, or both areoperationally interconnected for alternate operation to effect alock-stepping of out-of-phase operation of the respective pumpingelements.
 16. A pump apparatus according to claim 15, wherein theoperational interconnection is mechanical by means of respective commondouble-action actuators.
 17. A pump apparatus according to claim 1,wherein the first venturi forms part of a first ejector assemblyincluding a first elongate body having a first low-restriction upperchamber narrowing to a first accelerator tube, the venturi effect beingprovided by a first injector nozzle directing high pressure air from anair supply across the first upper chamber into the first acceleratortube, lowering the pressure in the first upper chamber.
 18. A pumpapparatus according to claim 17, wherein the first upper chamber is influid communication with the top portion of the first housing to effecta reduction in pressure in the first housing.
 19. A pump apparatusaccording to claim 17, wherein the air supply to the first injectornozzle is switched by an air control valve.
 20. A pump apparatusaccording to claim 19, wherein the air control valve is open throughboth the charge and discharge parts of the cycle, and is closed todisable the first pumping element when the first pumping element is notin operation.
 21. A pump apparatus according to claim 20, wherein thefirst ejector assembly includes a first cycling valve across the firstaccelerator tube or a venturi exhaust, the first cycling valve operableto alternately open the venturi exhaust to allow the first venturi tooperate and reduce pressure in the first housing, and to close theventuri exhaust path to stall the venturi, close off the venturi exhaustpath to the delivery line, and pressurize the first upper chamber andthe first housing.
 22. A pump apparatus according to claim 21, whereinlimit switches associated with the first material inlet and/or the firstdischarge outlet are used to ensure that the first material inlet and/orthe first discharge outlet are appropriately set before the controlleroperates the cycling valve.
 23. A pump apparatus according to claim 1,wherein the controller comprises a pneumatic controller.
 24. A pumpapparatus according to claim 23, wherein the controller comprises aprogrammable logic controller (PLC).
 25. A pump apparatus according toclaim 23, wherein the controller controls directly or indirectly any oneor more of the functions of charge volume control, discharge volumecontrol, pumping element on/off control, air pressure regulation, inletand outlet valve timing, venturi operation and housing pressurizationcontrol.
 26. A pump apparatus according to claim 25, wherein thecontroller controls the amount of material admitted to the firsthousing, the second housing, or both for each cycle by including a timerfunction.